[PATCH] drm/amdgpu: add the checking to avoid NULL pointer dereference

[Chunming Zhou]

在 2018/11/23 21:30, Koenig, Christian 写道:
> Am 23.11.18 um 14:27 schrieb Zhou, David(ChunMing):
>> 在 2018/11/22 19:25, Christian König 写道:
>>> Am 22.11.18 um 07:56 schrieb Sharma, Deepak:
>>>> when returned fence is not valid mostly due to userspace ignored
>>>> previous error causes NULL pointer dereference.
>>> Again, this is clearly incorrect. The my other mails on the earlier
>>> patch.
>> Sorry for I didn't get your history, but looks from the patch itself, it
>> is still a valid patch, isn't it?
> No, the semantic of amdgpu_ctx_get_fence() is that we return NULL when
> the fence is already signaled.
>
> So this patch could totally break userspace because it changes the
> behavior when we try to sync to an already signaled fence.
Ah, I got your meaning, how about attached patch?

-David
>
> If that patch was applied then please revert it immediately.
>
> Christian.
>
>> -David
>>> If you have already pushed the patch then please revert.
>>>
>>> Christian.
>>>
>>>> Signed-off-by: Deepak Sharma <Deepak.Sharma at amd.com>
>>>> ---
>>>>     drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 2 ++
>>>>     1 file changed, 2 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>>>> index 024dfbd87f11..14166cd8a12f 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
>>>> @@ -1403,6 +1403,8 @@ static struct dma_fence
>>>> *amdgpu_cs_get_fence(struct amdgpu_device *adev,
>>>>           fence = amdgpu_ctx_get_fence(ctx, entity, user->seq_no);
>>>>         amdgpu_ctx_put(ctx);
>>>> +    if(!fence)
>>>> +        return ERR_PTR(-EINVAL);
>>>>           return fence;
>>>>     }

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